Somewhere, deep in the statistical noise, there is a contribution from the global buildup of heat-trapping gases changing the climate system.

Among the clearest outcomes of global warming are hotter heat waves and having more of a season’s rain come in heavy downpours. But the picture gets murky, indeed nearly insoluble, at the scale of states or smaller regions. There’s more on this below from the Texas state climatologist and others. The bottom line is there’s no trend in Texas gullywashers.

What’s vividly clear is the extreme vulnerability created by the continuing development pulse in some of the state’s most hazardous places — including Hays County, in the heart of an area that weather and water agencies long ago dubbed “Flash Flood Alley.” (Here’s a great interactive explainer.)

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Hays County, Texas, one of the areas hardest hit by flooding on Memorial Day weekend, has seen extraordinary population growth in recent decades. Data are from Census.gov.Credit

The region’s population and building booms are far outpacing efforts to reduce exposure to flood dangers, resulting in long-predicted scenarios playing out at high cost in lives and money.

“The main challenge to rational planning for flood risk in the country is that private property rights trump even modest limitations on floodplain development,” said Nicholas Pinter, an expert on floods, people and politics at Southern Illinois University, in an email today. “And that sentiment runs deep in Texas. The result is unchecked construction on flood-prone land, up to the present day and in some places even accelerating.”

In Texas, there’s a “too little, too late” feel to the steps that have gotten under way — including a variety of United States Army Corps of Engineers studies of flood risk.

One such flood analysis, for the northern part of Hays County, begun in 2011 and is just now entering final review. The risk was laid out four years ago in an announcement of the study:

Hays County’s population has been increasing dramatically – the county’s population grew from 97,589 in 2000 to 157,107 in 2010, a 61% increase. Development has subsequently increased as well. This growth has the potential to place residents at a greater risk for human and economic losses from floods.

In a telephone interview, Randy Cephus, a public affairs official in the Corps’s Fort Worth district office, said this was a fast pace. “The Corps has gone through a transformation,” he said. “In the past, studies have taken 8 to 10 years to complete. We’re trying to undergo those within 3 years.”

It’s important to get these studies done, but I doubt they’ll have much impact as long as politicians and communities in the region stick with the go-go development mentality that has been so vividly on display.

I see little evidence that leaders in the region have paid attention to the vast volumes of information they already paid for. The websites of Texas agencies responsible for managing water and limiting disaster losses are already full of valuable information clearly laying out the deep hydrological vulnerability in the state.

A map in a 2005 flood safety report showing past extreme downpours in Texas, drawing on data from the United States Army Corps of Engineers.Credit Guadalupe-Blanco River Authority

In the meantime, most regional coverage of growth has centered on the economy, which is fine if it is meshed with environmental considerations and doesn’t lead to costly public bailouts when disaster strikes. (Google for

Here’s a KXAN web report from March on census data showing Austin’s growth lagging only Myrtle Beach in the Carolinas and a couple of retirement hubs in Florida.

The town was hit hard over the weekend. To see what a combination of sprawl and extreme flooding looks like, a good place to start is the drone video posted on YouTube by Stephen Ramirez, a photographer from San Marcos with a background in environmental science. Here’s an image, isolated from the video, showing the new Woods of San Marcos apartment complex.

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A new apartment complex in San Marcos, Tex., one of many fast-growing communities hit hard by flooding.Credit Stephen Ramirez/ Birdsiview.org

In an email exchange, Ramirez explained that the lack of resilience created in the region’s crowding flood zones has been accompanied by environmental impacts, as well:

There are a lot of citizens in the community who are extremely frustrated with the inappropriate locations of development within our watersheds. Recent and planned developments along the floodplain and riverfront of the San Marcos river, and the sensitive Edwards Aquifer recharge zone that feeds it, have been a heartbreaking loss for this community. We are sick of get-rich-quick developments that lack the foresight to maintain the quality of life and preserve our endangered natural resources.

There’s much more to write on the issues raised in Texas and so many other places where communities have yet to figure out a balanced relationship with environments, for the sake of both people and the planet. Stay tuned.

To close things out, here’s the promised deeper dive on flood and rainfall trends in the state in the context of global warming.

I queried several climatologists I know in Texas. Andrew Dessler at Texas A&M encouraged me to ask John W. Nielsen-Gammon, the state climatologist. He offered these thoughts and studies, which, in the aggregate, point to no robust trend either in extreme downpours or extreme stream flows:

Villarini and Smith looked at changes in extreme flows in 62 gauges with record lengths of at least 70 years, and found 2 with statistically significant increases and two with statistitcally significant decreases.

One of the most important reasons we care about climate change is because it exacerbates the risks we already face today. Texas is home to many of the fastest growing metro areas in the U.S. This rapid urbanization and development changes the face of the land, increasing flood risk at a time when, at least for the eastern half of the state, the risk of heavy downpours is also on the rise.

This is not my research area so my comments are anecdotal. But I have lived in Texas all my life and have witnessed this over and over. First, Texas is absolutely pro-development and this can create both short-term issues and long-term ones as well. In the short term, the developer pushes the limit in terms of building in flood plains and there is often little resistance. But in the longer term, even if the developer stayed away from existing flood plains, future development changes the flood patterns. So a home that was not in danger 20 years ago is now in danger because a shopping center has paved over 40 acres of land that once absorbed runoff. That runoff is now headed downstream.

Second, flood protection is often to protect business interests and not residential. Case in point, the levees on the Trinity River than runs just south of downtown Dallas. The levees begin a few miles west of downtown and end just east. The levees were built after a flood on the Trinity that inundated downtown. A current example of lack of foresight on the part of planners is the dream of some civic leaders to build a toll road in the flood basin of the Trinity.

Third, Nicholas [Pinter, cited in post above] is right that we flood more than we want to admit. We live north of Dallas-Fort Worth, close to Lake Texoma. When the dam was built, it was estimated that water would only go over the spillway once in 100 years. Well, it has done that 4 times in the last 58, twice since we’ve lived here — 2007 and now this year.

Developers like to “move some dirt’ in the Texas vernacular. They have a great deal of power. Dallas-Fort Worth is exploding in population right now. Every new subdivision or shopping center has an impact on the safety of people and property downstream. We should learn from each flooding event but I’m not sure that we do.

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By 2050 or so, the human population is expected to pass nine billion. Those billions will be seeking food, water and other resources on a planet where humans are already shaping climate and the web of life. Dot Earth was created by Andrew Revkin in October 2007 -- in part with support from a John Simon Guggenheim Fellowship -- to explore ways to balance human needs and the planet's limits.